Mounting Evidence for an Expanded Host Range of Influenza B Viruses

Influenza B viruses (IBV) belong to the family of <i>Orthomyxoviridae</i> and circulate annually in humans causing respiratory illness. Although they are considered an exclusively human pathogen, there is evidence of IBV infections in animals, including wildlife, companion animals and livestock. In addition, metagenomic studies have identified novel orthomyxoviruses in amphibians and fish that appear related to IBV, suggesting influenza viruses, including IBV, have been associated with vertebrates across their evolutionary history. In this review, we summarise our current knowledge of potential IBV and IBV-like infections in animals. These collectively suggest that the ecology of IBV extends beyond humans and warrants further investigations.